First, could you squeeze more fuel in the descent stage? There is certainly room (see below). Then how about mass margin?
Instead, JPL could use the pressurization sequence to move liquid fuel from tank to tank, changing the center of gravity, then move it back again.
This would reduce the needed ejectable masses
A bi-propellant descent stage would only need 300 kg of propellant as opposed to the 400 kg they used. (Plus the tanks would be lighter both due to smaller size and lower pressure -
Finally, their descent profile is designed to be as safe as possible, not to use the minimum fuel. A more hoverslam-type landing would use less fuel, leaving more for post-rover-dropoff maneuvers.
SpaceX's plans are irrelevant to any future Skycrane developments. I think your point may be retro-propulsive landings will obsolete everything else. Maybe...maybe not...that is a possibility, however current missions like sample return are paced towards later this decade.
<snip>SpaceX's plans are irrelevant to any future Skycrane developments. <snip>Even if SpaceX succeeded with landing on Mars tomorrow, nothing is in the NASA, ESA, JAXA or any other agencies pipeline for science missions that would take advantage of that. ( I could be unaware of it , but haven't heard of anything)
Once again, I don't think these changes are a good idea. But there is certainly slack in the system - the descent stage had reliability in mind, not the utmost possible performance.
Quote from: LouScheffer on 02/28/2021 11:38 pmFinally, their descent profile is designed to be as safe as possible, not to use the minimum fuel. A more hoverslam-type landing would use less fuel, leaving more for post-rover-dropoff maneuvers. Wrong. A hover slam does not save propellant. It is used when the engines can't throttle low enough and still have a T/W>1. It actually uses more propellant because a larger than necessary engines are used. [...]
At the beginning (Red Dragon ?) Musk wanted to go 100% propulsive, just like on the Moon - and a bit like Falcon 9, using retropropulsive rocketry (note: the paper mentions supersonic retro-propulsion, nearly a decade before Falcon 9 2013-2016 gradual mastering of it !) Doing as if Mars atmosphere was thin enough, it simply did not existed. But Mars atmosphere did not agree, and would readily burn any such lander. Alternatively, it would burden it with an enormous amount of propellant. In both cases: Mars versus Musk: 1-0 for Mars. Even Musk had to concede to Mars, and accept some hypersonic glide. In turn, this led to the present SN-8 / SN-9 flight profile - with the skydive manoeuver, and hypersonic entry / glide, Shuttle style. Except there is no Shuttle Landing Strip on Mars, so back to a vertical landing... Mars EDL is hard, because Mars is so damn unforgiving.
Little note regarding Red Dragon: they inverted the angle of attack, so they used the aerodynamic forces pointing down. This allowed them to bleed more energy. How? Because to get more time of atmosphere drag, they needed shallow entry angles, but at those speed they would skip over the atmosphere. So, by inverting the angle of attack they actually avoided skipping and could bleed more speed.I do wonder if they will use a similar trick with Starship.
So I would like to know how "independent" were/are it's capabilities from the Rovers which it lowered to the surface?
Skycrane is the only available and proven technology that can put something on the surface of Mars.
I'm hoping that someone is still monitoring this tread... I'm coming in from the "Will a Starship head to Mars in the 2024 launch window" thread.. I need some help on Skycrane capabilities, who designed, and can I get one for a Starship mission to Mars. Skycrane is the only available and proven technology that can put something on the surface of Mars. So I would like to know how "independent" were/are it's capabilities from the Rovers which it lowered to the surface? And possibly a few other questions like could it work with the ESA Rover? Thx.
Do you think JPL would be onboard for making more and adding the necessary smarts? In time for 2024 mission?They should also change their disposal method from "flyaway and litter the surface" to "flyaway and neatly land"?Do you think two years is enough time for ESA to convert ExoMars Rover into a Descent Stage package?
Hi Jim, long time no see... Actually, Jim and I met recently on the Orion thread, and there he told me there was no such thing as skycrane. Imagine my surprise when I can across a thread called, "Skycrane future developments discussion thread". and even bigger surprise to find him here.But all jesting aside, appreciate the responses. I did kind of suspect that Perserverance had all the smarts. So, one of the things appropriate for this thread is how to turn the "descent stage" into a more "general purpose" Mars cargo delivery system - doubt that NASA will want to rely solely on Starship to drop things on the surface - by adding the sensors, nav and landing smarts into the descent stage (see Jim, I called it descent stage and not skycrane Do you think JPL would be onboard for making more and adding the necessary smarts? In time for 2024 mission?They should also change their disposal method from "flyaway and litter the surface" to "flyaway and neatly land"?Do you think two years is enough time for ESA to convert ExoMars Rover into a Descent Stage package?
3) What benefit is there from soft landing the descent stage? MSL and Perseverance were launched by expendable vehicles, everything except the payload is discarded along the way. Why single out the descent stage for special treatment?